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Vincent M Christoffels

Publications and source records attributed to Vincent M Christoffels.

At least 19 recordsLinked to original sources
PubMed2026

Whole-genome sequencing implicates rare, low-frequency and structural non-coding variation at the SCN5A locus in Brugada syndrome.

Brugada syndrome (BrS) is an inherited cardiac condition characterized by a hallmark ECG pattern and an increased risk of sudden cardiac death. Central to the aetiology of BrS, the SCN5A region harbours both common non-coding risk variants and rare coding variants that are causative in approximately 20% of patients. However, rare non-coding genetic variation in this region remains largely unexplored. Here, we used whole-genome sequencing (WGS) of 752 European-ancestry BrS cases and 1,827 ancestry-matched controls to identify BrS-associated rare non-coding genetic variation at the SCN5A locus. Sliding-window and cis-regulatory element (CRE)-based rare-variant aggregate testing implicated three conserved CREs, including a dense aggregation of case singleton variants within a 178 bp enhancer in intron 17 of SCN5A which replicated in an independent BrS cohort. Prioritised BrS-associated rare and low-frequency non-coding variants within these elements were predicted to alter cardiac transcription factor motifs, and altered CRE activity in hiPSC-CM luciferase assays or were associated with BrS-relevant ECG endophenotypes in the UK Biobank. Single-variant analysis across the region identified a Bonferroni-significant five-fold case-enriched low-frequency variant within a known CRE in intron 1 of SCN5A, which replicated, was associated with slower cardiac conduction in the UK Biobank and accounted for part of the BrS GWAS signal at this locus. Structural variant analyses identified a 10.5 kb deletion upstream of SCN5A in a BrS case that encompassed a cardiac CRE and reduced sodium current density in a hiPSC-CM model, as well as a 6 kb BrS-enriched retrotransposon insertion in SCN5A that appeared to underlie part of the GWAS signal in this region. Together, these findings implicate rare and low-frequency non-coding variation at the SCN5A locus in BrS susceptibility and demonstrate the value of targeted WGS analysis of key disease loci.

Journal Article↗
PubMed2025

AAV6 vectors provide superior gene transfer compared to AAV9 vectors following intramyocardial administration.

Cardiac gene therapy using adeno-associated viral (AAV) vectors holds great promise for treating heart diseases but would benefit from more potent AAV vectors. Vectors based on the AAV serotypes 6 and 9 have been used in pre-clinical gene therapy studies, yet the therapeutic outcomes varied depending on the experimental model and delivery route used. Here, we evaluated the transduction efficiency of AAV6, AAV9, and AAV9-derived MyoAAVs for local cardiac delivery. Vectors were tested in neonatal rat ventricular myocytes, and subsequently in mouse hearts by direct intramyocardial injection. Vector genome levels, mRNA expression levels, and fluorescence were measured. The AAV6 and AAV9 vectors were further validated in porcine hearts, human-induced pluripotent stem-cell-derived cardiomyocytes, and human atrial myocardial slices. In both rat cardiomyocytes and mouse hearts, AAV6 exhibited the highest transduction efficiency. Direct comparison of the AAV6 and AAV9 vectors in porcine and human models confirmed that AAV6 is more potent. In conclusion, AAV6 vectors are superior to AAV9 and its derivative vectors for cardiac transduction by direct intramyocardial injection. In addition, the in vivo transduction efficiency correlates with in vitro and ex vivo assays, thereby facilitating the development of more potent AAV variants for cardio-selective delivery methods.

AAV vector↗
PubMed2006

Two distinct pools of mesenchyme contribute to the development of the atrial septum.

Closure of the primary atrial foramen is achieved by fusion of the atrioventricular cushions with the mesenchymal cap on the leading edge of the muscular primary atrial septum. A fourth component involved is the vestibular spine, originally described by His in 1880 as an intra-cardiac continuation of the extra-cardiac mesenchyme of the dorsal mesocardium. The morphogenesis of this area is of great clinical interest, because of the high incidence of atrial and atrioventricular septal defects. Nonetheless, the origin of the participating components is largely unknown. Here we report that the primary atrial foramen is surrounded in its entirety by mesenchyme derived from endocardium. A second population of mesenchyme not derived from endocardium was observed at the caudal margin of the mesenchymal atrial cap, entirely embedded within the mesenchyme derived from endocardium and contiguous with the mesenchyme of the dorsal mesocardium. Our reconstructions show this second population does indeed take the form of a short spine, albeit that it is the right pulmonary ridge, rather than this spine, that protrudes into the atrial lumen. From the stance of morphological description, therefore, there is little thus far to substantiate the existence of an atrial spine.

Embryonic Development↗
PubMed2006

Formation of the venous pole of the heart from an Nkx2-5-negative precursor population requires Tbx18.

The venous pole of the mammalian heart is a structurally and electrically complex region, yet the lineage and molecular mechanisms underlying its formation have remained largely unexplored. In contrast to classical studies that attribute the origin of the myocardial sinus horns to the embryonic venous pole, we find that the sinus horns form only after heart looping by differentiation of mesenchymal cells of the septum transversum region into myocardium. The myocardial sinus horns and their mesenchymal precursor cells never express Nkx2-5, a transcription factor critical for heart development. In addition, lineage studies show that the sinus horns do not derive from cells previously positive for Nkx2-5. In contrast, the sinus horns express the T-box transcription factor gene Tbx18. Mice deficient for Tbx18 fail to form sinus horns from the pericardial mesenchyme and have defective caval veins, whereas the pulmonary vein and atrial structures are unaffected. Our studies define a novel heart precursor population that contributes exclusively to the myocardium surrounding the sinus horns or systemic venous tributaries of the developing heart, which are a source of congenital malformation and cardiac arrhythmias.

Animals↗
PubMed2006

Left and right ventricular contributions to the formation of the interventricular septum in the mouse heart.

Mammalian heart development involves complex morphogenetic events which lead to the formation of fully separated left and right atrial and ventricular chambers from a tubular heart. Separation of left and right ventricular chambers is dependent on a single structure, the interventricular septum (IVS), which has both muscular and mesenchymal components. Little is known about the morphogenetic events that lead to the formation of the muscular component of the IVS. We have analyzed two transgenic mouse lines that display complementary nlacZ reporter gene expression patterns in the embryonic ventricles: the Mlc1v-nlacZ-24 transgene is expressed in right ventricular myocardium and the Mlc3f-nlacZ-2 transgene in left ventricular myocardium. Detailed analysis of these transgene expression patterns during IVS formation reveals a symmetric left and right myocardial identity within the developing IVS between embryonic days 9.5 and 11.5. From embryonic day 12.5 onwards, myocytes with a left ventricular identity dominate the IVS, particularly in its dorsal aspect. The T-box transcription factor encoding gene, Tbx18, is expressed in the left ventricle and left side of the developing IVS, providing additional support for the presence of left and right ventricular identities within the IVS. Analysis of clonally related cardiomyocyte clusters confirms that both left and right ventricular myocardial cell populations contribute to the forming IVS, in similar domains to those defined by the Mlc-nlacZ transgenes. Examination of the orientation as well as the distribution of labeled cells in clusters provides new insights into the morphogenesis of the septum.

Animals↗
PubMed2005

Expression and regulation of the atrial natriuretic factor encoding gene Nppa during development and disease.

The endocrine function of the heart was shown by the identification of a potent inhibitor of renal tubular NaCl reabsorbtion, atrial natriuretic peptide/factor (ANP), in atrial extracts. Since then, Nppa, the gene encoding ANP, has become an important tool for molecular and developmental biologists. Expression of Nppa is an early and specific marker for the differentiating working myocardium of the atria and ventricles of the developing heart. Around the time of birth, ventricular Nppa expression is down-regulated, to be reactivated in response to a variety of cardiovascular disorders. Many aspects of the regulatory pathways that control Nppa gene expression during cardiac development or disease have been revealed. However, several fundamental issues remain to be resolved. Particularly, the regulatory mechanisms underlying the ventricular Nppa expression in the embryonic heart and the reactivation in the failing ventricle remain unclear. Here we review current knowledge on the transcriptional regulation of the Nppa gene.

Animals↗
PubMed2005

Tbx20 is essential for cardiac chamber differentiation and repression of Tbx2.

Tbx20, a member of the T-box family of transcriptional regulators, shows evolutionary conserved expression in the developing heart. In the mouse, Tbx20 is expressed in the cardiac crescent, then in the endocardium and myocardium of the linear and looped heart tube before it is restricted to the atrioventricular canal and outflow tract in the multi-chambered heart. Here, we show that Tbx20 is required for progression from the linear heart tube to a multi-chambered heart. Mice carrying a targeted mutation of Tbx20 show early embryonic lethality due to hemodynamic failure. A linear heart tube with normal anteroposterior patterning is established in the mutant. The tube does not elongate, indicating a defect in recruitment of mesenchyme from the secondary heart field, even though markers of the secondary heart field are not affected. Furthermore, dorsoventral patterning of the tube, formation of working myocardium, looping, and further differentiation and morphogenesis fail. Instead, Tbx2, Bmp2 and vinexin alpha (Sh3d4), genes normally restricted to regions of primary myocardium and lining endocardium, are ectopically expressed in the linear heart tube of Tbx20 mutant embryos. Because Tbx2 is both necessary and sufficient to repress chamber differentiation (Christoffels et al., 2004a; Harrelson et al., 2004), Tbx20 may ensure progression to a multi-chambered heart by repressing Tbx2 in the myocardial precursor cells of the linear heart tube destined to form the chambers.

Animals↗
PubMed2005

Comparative analysis of the natriuretic peptide precursor gene cluster in vertebrates reveals loss of ANF and retention of CNP-3 in chicken.

We identified and characterized the chicken natriuretic peptide precursor gene cluster and found its organization to be highly conserved compared with the mammalian Nppb-Nppa cluster. However, phylogenetic analysis indicated that the putative chicken natriuretic peptide precursor genes are the homologues of CNP-3 and Nppb, respectively. Comparative expression analysis revealed that, in human, mouse, and rat hearts, Nppb is a novel marker for the differentiating working myocardium. Its expression pattern is strikingly similar to that of Nppa before birth, and diverges only after birth. In contrast, whereas the chicken Nppb gene expression profile resembled that of mammalian Nppb, the CNP-3 gene showed very limited expression in the heart, not resembling the pattern of either Nppa or Nppb. These results show that, in chicken, the Nppa gene has been lost from the natriuretic peptide precursor gene cluster, whereas the CNP-3 gene has been retained.

Amino Acid Sequence↗
PubMed2005

Inactivation of the Sema5a gene results in embryonic lethality and defective remodeling of the cranial vascular system.

The semaphorins are a large family of proteins involved in the patterning of both the vascular and the nervous systems. In order to analyze the function of the membrane-bound semaphorin 5A (Sema5A), we generated mice homozygous for a null mutation in the Sema5a gene. Homozygous null mutants die between embryonic development days 11.5 (E11.5) and E12.5, indicating an essential role of Sema5A during embryonic development. Mutant embryos did not show any morphological defects that could account for the lethality of the mutation. A detailed analysis of the vascular system uncovered a role of Sema5A in the remodeling of the cranial blood vessels. In Sema5A null mutants, the complexity of the hierarchically organized branches of the cranial cardinal veins was decreased. Our results represent the first genetic analysis of the function of a class 5 semaphorin during embryonic development and identify a role of Sema5A in the regional patterning of the vasculature.

Animals↗
PubMed2004

Lineage and morphogenetic analysis of the cardiac valves.

We used a genetic lineage-labeling system to establish the material contributions of the progeny of 3 specific cell types to the cardiac valves. Thus, we labeled irreversibly the myocardial (alphaMHC-Cre+), endocardial (Tie2-Cre+), and neural crest (Wnt1-Cre+) cells during development and assessed their eventual contribution to the definitive valvar complexes. The leaflets and tendinous cords of the mitral and tricuspid valves, the atrioventricular fibrous continuity, and the leaflets of the outflow tract valves were all found to be generated from mesenchyme derived from the endocardium, with no substantial contribution from cells of the myocardial and neural crest lineages. Analysis of chicken-quail chimeras revealed absence of any substantial contribution from proepicardially derived cells. Molecular and morphogenetic analysis revealed several new aspects of atrioventricular valvar formation. Marked similarities are seen during the formation of the mural leaflets of the mitral and tricuspid valves. These leaflets form by protrusion and growth of a sheet of atrioventricular myocardium into the ventricular lumen, with subsequent formation of valvar mesenchyme on its surface rather than by delamination of lateral cushions from the ventricular myocardial wall. The myocardial layer is subsequently removed by the process of apoptosis. In contrast, the aortic leaflet of the mitral valve, the septal leaflet of the tricuspid valve, and the atrioventricular fibrous continuity between these valves develop from the mesenchyme of the inferior and superior atrioventricular cushions. The tricuspid septal leaflet then delaminates from the muscular ventricular septum late in development.

Animals↗
PubMed2004

The transcriptional repressor Tbx3 delineates the developing central conduction system of the heart.

OBJECTIVE: The molecular mechanisms that regulate the formation of the conduction system are poorly understood. We studied the developmental expression pattern and functional aspects of the T-box transcription factor Tbx3, a novel marker for the murine central conduction system (CCS). METHODS: The patterns of expression of Tbx3, and of Cx40, Cx43, and Nppa, which are markers for atrial and ventricular chamber-type myocardium in the developing heart, were analyzed in mice by in situ hybridization and three-dimensional reconstruction analysis. The function of Tbx3 in regulating Nppa and Cx40 promoter activity was studied in vitro. RESULTS: In the formed heart, Tbx3 is expressed in the sinoatrial node (SAN), atrioventricular node (AVN), bundle and proximal bundle branches (BBs), as well as the internodal regions and the atrioventricular region. Throughout cardiac development, Tbx3 is expressed in an uninterrupted myocardial domain that extends from the sinoatrial node to the atrioventricular region. This expression domain is present in the looping heart tube from E8.5 onwards. Expression of the chamber-type myocardial markers is specifically absent from the Tbx3 expression domain. Tbx3 is able to repress Nppa and Cx40 promoter activity and abolish the synergistic activation of the Nppa promoter by Tbx5 and Nkx2.5. CONCLUSION: We identified the T-box transcription factor Tbx3 as a novel and accurate marker for the central conduction system. Our analysis implicates a role for Tbx3 in repressing a chamber-specific program of gene expression in regions from which the components of the central conduction system are subsequently formed.

Animals↗
PubMed2004

Controversies concerning the anatomical definition of the conduction tissues.

Conduction across the atrioventricular junctions had long been controversial, with arguments raging as to whether such conduction was myogenic or neurogenic. The landmark study of Tawara in 1906 established the existence of an axis of histologically specialized myocardial cells contained within fibrous sheaths as being responsible for rapid conduction from the atrial to the ventricular myocardium. Keith and Flack then demonstrated that the atrial impulse was generated in the sinus node, with subsequent slowing within the atrioventricular node of Tawara. The detailed reviews of Aschoff and Monckeberg then emphasized the morphological features that permit unequivocal recognition of the nodes, along with rapidly conducting tracts. It is now pertinent that we remember these original criteria for anatomical recognition as we discuss the steps involved in the development of these conducting structures from their embryologic primordiums. In this review, we restate the criteria of Aschoff and Monckeberg, then discuss their relevance to the developmental issues, emphasizing that all myocardial cells have the potential to conduct. The important issues, therefore, are the changes that occur as the heart itself changes from a solitary muscular tube, already possessing the capacity t generate an electrocardiogram, to the four-chambered structure we recognize in postnatal life.

Animals↗
PubMed2004

T-box transcription factor Tbx2 represses differentiation and formation of the cardiac chambers.

Specific regions of the embryonic heart tube differentiate into atrial and ventricular chamber myocardium, whereas the inflow tract, atrioventricular canal, inner curvatures, and outflow tract do not. These regions express Tbx2, a transcriptional repressor. Here, we tested its role in chamber formation. The temporal and spatial pattern of Tbx2 mRNA and protein expression in mouse hearts was found to be complementary to that of chamber myocardium-specific genes Nppa, Cx40, Cx43, and Chisel, and was conserved in human. In vitro, Tbx2 repressed the activity of regulatory fragments of Cx40, Cx43, and Nppa. Hearts of transgenic embryos that expressed Tbx2 in the prechamber myocardium completely failed to form chambers and to express the chamber myocardium-specific genes Nppa, Cx40, and Chisel, whereas other cardiac genes were normally expressed. These findings provide the first evidence that Tbx2 is a determinant in the local repression of chamber-specific gene expression and chamber differentiation.

Animals↗
PubMed2004

Architectural plan for the heart: early patterning and delineation of the chambers and the nodes.

During folding of the embryo, lateroanterior visceral mesoderm forms the embryonic tubular heart at the midline, just ventral to the foregut. In mice, this nascent tube contains the future left ventricle and atrioventricular canal. Mesenchymal cells subsequently recruited to the cardiac lineage at the intake and the outflow of the tube will form the atria and the right ventricle and outflow tract, respectively. Shortly after its emergence, the embryonic heart tube starts to loop, and the first signs of left ventricular chamber differentiation become visible on the outer curvature of the middle portion of the tube. Subsequently, the right ventricle differentiates cranially, and the atria caudally, while the inflow tract, atrioventricular canal, inner curvatures, and outflow tract form recognizable components flanking the chambers. The latter, nonchamber regions in turn provide signals for the formation of the cushion mesenchyme, are involved in remodeling of the heart, and form the nodes of the conduction system. This review discusses how the patterning of the heart tube relates to the localized differentiation of atrial and ventricular chambers, why some parts of the heart do not form chambers, and how this relates to the formation of the conduction system.

Animals↗
PubMed2004

Vasopressin-induced vasoconstriction is dependent on MAPKerk1/2 phosphorylation.

To investigate the involvement of the mitogen-activated protein kinase (MAPK) family of extracellular signal-regulated kinase (ERK) 1 and 2 (MAPKerk1/2) in the vasopressin-mediated vasoconstriction in the rat aorta. Vasopressin-induced vasoconstriction was measured in isolated rat thoracic aortae in the presence or absence of MAPKerk1/2 kinase (MKKmek1/2) inhibitors. Thereafter the MAPKerk1/2 phosphorylation in the rat aorta was quantified using Western blot analysis. Vasopressin (1-300 nm) induced a concentration-dependent vasoconstriction, which could be inhibited concentration dependently by the selective MKKmek1/2 inhibitors, PD 98059 (10 and 100 microm) and U 0126 (10 and 100 microm). Western blot analysis revealed a 2.7 +/- 0.6-fold increase in the MAPKerk1/2 phosphorylation induced by vasopressin (300 nm). This phosphorylation could be dose dependently prevented by both PD 98059 (100 microm) and U 0126 (10 and 100 microm). These results indicate that vasoconstriction induced by vasopressin is partly regulated by the MAPKerk1/2 pathway.

Animals↗
PubMed2004

Development of the building plan of the heart.

In this communication we discuss the formation of the synchronously contracting chambered heart from a peristaltically contracting linear heart tube. It is proposed that members of the T-box family of transcription factors play a crucial role in the formation of the building plan of the formed heart. Tbx5 may confer venoarterial polarity to the heart tube, whereas Tbx2 initially and Tbx3 in later developmental stages prevent the cardiac inflow tract, atrioventricular region, outflow tract, as well as the cardiac inner curvatures from chamber differentiation. With the exception of the outflow tract that becomes incorporated into the ventricles, these regions contribute to the cardiac conduction system.

Body Patterning↗
PubMed2003

Regulatory modules in the developing heart.

Fragments of regulatory DNA of cardiac genes drive reporter gene expression in sometimes unexpected subdomains of the heart. These patterns have revealed that the regulatory DNA of genes consists of distinct subfragments (regulatory modules) that are active in different regions of the developing heart. In this review we give an overview of the activity of regulatory modules in vivo. Furthermore, we investigated the relationship between the activity domains of the regulatory modules, the building blocks of the heart and the developmental patterning of the myocardium. Most of the regulatory modules show a domain of activity broader than the morphological boundary of a cardiac compartment and seem to respond to a patterning program along the antero-posterior axis.

Animals↗